The increasing generation of electricity from renewable, fluctuating sources of energy (solar and wind energy) may occasion periods in which the rate of electricity generation exceeds the contemporaneous rate of electricity consumption. The then inexpensively available surplus electricity can be used in such periods to produce, for example, hydrogen via a hydrogen electrolysis. Adding a carbon source, for example carbon dioxide CO2, will then also make possible the production of synthesis products such as methanol. The chemical reaction used for this is as follows:CO2+3 H2->CH3OH+H2O  (reaction formula 1)
The chemical equilibrium in this reaction is largely on the left-hand side, resulting under customary reaction conditions of 200 to 300° C. and 30 to 80 bar pressure in but a very low degree of conversion for the starting materials passing through the reactor. Increasing the reaction pressure, however, causes the reaction equilibrium to shift to the right-hand side, as known from Tidona, B. et al. (2013), “CO2 hydrogenation to methanol at pressures up to 950 bar”, Journal of Supercritical Fluids 78, pp. 70-77. Even just a pressure of about 300 bar will cause a nearly complete displacement of the reaction equilibrium onto the side of the products, methanol and water. High conversions are thus achieved for a single pass through the synthesis reactor. Being in liquid form, the reaction products of methanol and water are withdrawable from the equilibrium-limited methanol synthesis reaction in a continuous manner. The process described is disadvantageous because the high energy requirements for compressing the hydrogen and carbon dioxide starting materials to the desired pressure make commercial practice distinctly unattractive. The same problem also presents with other chemical types of synthesis processes where liquid products are formed under high pressure.